1. Field of the Invention
The present invention relates to bicycles having a front fork wheel suspension. More particularly, the present invention is directed to improvements which will enable a bicycle front fork wheel suspension to be more readily adapted to the needs of a wider variety of riders, and to modifications which are designed to improve handling characteristics of bicycles having front fork wheel suspensions.
2. Description of Related Art
In the present inventor's U.S. Pat. No. 4,971,344, a bicycle having a telescopic suspension system for the front wheel is disclosed which allows the bicycle to perform in the manner of one having a standard, rigid front fork under normal riding conditions, so that the pedaling energy of the rider is not absorbed by the suspension system, yet it is also able to compress and absorb high input impact shocks as occur when the front wheel contacts pot holes, tree roots or rocks, etc. This characteristic is achieved through the use of a fluid-containing circuit that acts to lock the telescoping suspension assembly against compression by resisting low input forces imposed upon the fork, via handlebar and frame portions of the bicycle, as a result of a pedaling action of a rider of the bicycle, while enabling compression of the suspension assembly for absorption of impact shocks imposed upon the front fork by a wheel carried thereby by reacting under the effect of high input forces. In accordance with a preferred embodiment, the fluid-containing circuit includes a valve with a valve body having at least one flow port and a displaceable valve plate. The valve plate is spring loaded into a position in which it blocks fluid flow through the port, and which opens to permit fluid flow when the spring force on the plate is overcome.
In another aspect of the front fork wheel suspension of the applicant's earlier U.S. patent, a cross member interconnects the lower tube of each of a pair of telescoping suspension assemblies to limit twisting and rotating motion of the suspension assemblies. This cross member also serves to provide a brake cable stop which enables a front brake cable to float with the lower tubes of the telescoping assemblies. Additionally, a wheel rim brake is carried by the lower telescoping tubes in areas at which the cross member connects to the lower telescoping tubes so as to enable the rim brake to travel with the lower telescoping tubes.
While this front fork wheel suspension of the present inventor has proved to provide excellent performance (having been used by professional riders to win championships), and has been commercially successful, areas for further improvement have been noted. In particular, in this earlier suspension assembly, the spring force for the spring preloading of the valve plate was set to be correct for riders of average weight and riding ability, but was either too stiff or soft for riders who varied from the norm. To adjust the suspension for riders of different weight, the suspension system was pressurized with air through an air valve, and this air pressure could be altered to compensate for different rider weights or riding conditions. However, because the extension damping performance of the suspension is directly related to the amount of air pressure in the system, adjusting the air pressure to compensate for a rider's weight could adversely impact on the extension damping characteristics of the suspension.
Additionally, while the inverted U-shaped cross member was designed to resist the torsional forces placed on the fork between the handlebars and the front wheel, to limit twisting and rotation of the lower telescoping tubes, other forces acting on the fork were not taken into consideration. In particular, subsequent research and testing has shown that side loading forces are imposed during cornering or when the rider is climbing hills out of the saddle ("jamming"). These forces tend to cause the individual telescoping legs to move independently of each other, which can detract from the bicycle's handling characteristics.